JP6850165B2 - Pneumatic tires - Google Patents

Description

The present invention relates to a pneumatic tire.

Pneumatic tires with a row of blocks on the tread are prone to heel-and-toe wear, where one of the stepping side and the kicking side of the block wears more than the other. On the other hand, various structures for preventing heel-and-toe wear have been conventionally proposed. For example, in the pneumatic tire of Patent Document 1, the sipe formed in the block is provided with a narrow portion on the tread side and a wide portion on the inner side in the radial direction of the tire. Then, the shape of the wide portion changes from one end of the sipe toward the other end, and when the wide portion appears on the tread due to the progress of wear, the angle is changed.

By the way, the rigidity of the block is related to the heel-and-toe wear. Conventionally, various structures for ensuring rigidity have also been proposed. For example, in Patent Document 2, in order to secure rigidity, a locking region is provided inside the sipe so as to narrow the width of the sipe.

Japanese Unexamined Patent Publication No. 2011-183952 JP-A-2009-528946

The present invention has been made in view of such circumstances, and an object of the present invention is to provide a new pneumatic tire in which heel-and-toe wear is less likely to occur.

In the pneumatic tire of the embodiment, a plurality of blocks are arranged in the tire circumferential direction in a land portion defined by a main groove extending in the tire circumferential direction, and a lateral groove between blocks adjacent to the tire circumferential direction is 20% of the main groove. A sipe having a depth of 35% or less and narrower than the lateral groove is provided on the bottom side of the lateral groove, and the lateral groove extends diagonally with respect to the tire width direction, whereby one side of the block in the tire width direction is provided. An acute-angled corner is formed on the tire and an obtuse-angled corner is formed on the other side. As the sipe becomes deeper, the tire on the acute-angled corner side inclines in a direction away from the acute-angled corner, and the tire on the obtuse-angled corner side. It is characterized in that it is inclined in the direction of entering under the corner of the tire and is twisted by it.

In the pneumatic tire of the embodiment, the depth of the lateral groove is within a predetermined range, and a sipe narrower than the lateral groove is provided on the bottom side of the lateral groove, so that the rigidity of the block is increased and the block is heel-and-toe worn. Is less likely to occur.

The tread pattern of the pneumatic tire of the embodiment. FIG. 1 is a cross-sectional view taken along the line AA of FIG. FIG. 1 is a cross-sectional view taken along the line BB of FIG. FIG. 1 is a cross-sectional view taken along the line CC of FIG. Modified tread pattern. An example of changing the cross-sectional view taken along the line AA of FIG. Cross-sectional views of the lateral grooves and sipes of Examples , Reference and Comparative Examples in the tire width direction. (A) The figure of Comparative Example 1. (B) FIG. 2 of Comparative Example 2. (C) The figure of reference example 1. (D) The figure of reference example 2. (E) The figure of Example 1. (F) The figure of reference example 3.

The pneumatic tire of the embodiment will be described with reference to the drawings. The drawings may be exaggerated from the actual ones for the sake of explanation.

The pneumatic tire of the embodiment is mounted on a vehicle such as a light truck. The structure of the pneumatic tire of the embodiment is not limited except for the tread 10. The rough structure of the pneumatic tire of the embodiment is as follows. First, bead portions are provided on both sides in the tire width direction, and the carcass is folded back from the inside to the outside in the tire width direction to wrap the bead portion and form the skeleton of the pneumatic tire. A belt layer and a belt reinforcing layer are provided on the outer side in the tire radial direction of the carcass, and a tread 10 having a ground contact surface is provided on the outer side in the tire radial direction. In addition, sidewalls are provided on both sides of the carcass in the tire width direction. In addition to these members, a plurality of members are provided as required for the function of the tire.

The tread 10 shown in FIG. 1 is provided with three main grooves 11 extending in the tire circumferential direction. Divided into these main grooves 11, two left and right center land portions 20 and 40 near the tire equator CL and two left and right shoulder land portions 12 and 13 are formed.

Here, the center land portion 20 on the right side will be described as an example.

The center land portion 20 on the right side is provided with a narrow groove 30 extending in the tire circumferential direction. The narrow groove 30 is narrower than the main groove 11. The specific value of the width of the narrow groove 30 is, for example, 2 mm or more and 4 mm or less. The depth of the narrow groove 30 is 20% or more and 35% or less of the depth of the main groove 11. The center land portion 20 is divided into left and right by a narrow groove 30.

In the center land portion 20, a plurality of lateral grooves 31 and 32 are arranged alternately with the narrow groove 30 interposed therebetween. On the tire equatorial CL side of the narrow groove 30, the land portion is divided by a plurality of lateral grooves 31, so that a block row in which a plurality of center-side blocks 21 are arranged in the tire circumferential direction is formed. On the ground contact end E side of the narrow groove 30, the land portion is divided by a plurality of lateral grooves 32, so that a block row in which a plurality of shoulder side blocks 26 are arranged in the tire circumferential direction is formed. The plurality of center-side blocks 21 and the plurality of shoulder-side blocks 26 are arranged alternately with the narrow groove 30 interposed therebetween.

The lateral grooves 31 and 32 extend diagonally with respect to the tire width direction. The center side block 21 has a substantially parallelogram shape due to the plurality of lateral grooves 31 extending in parallel, and the shoulder side block 26 has a substantially parallelogram shape due to the plurality of lateral grooves 32 extending in parallel. Since the lateral grooves 31 and 32 extend diagonally with respect to the tire width direction, the center side block 21 and the shoulder side block 26 are formed with acute-angled corners 22 and obtuse-angled corners 23 on both sides in the tire circumferential direction, respectively. ing. In two blocks adjacent to each other in the tire circumferential direction, the acute-angled corners 22 of one block face the obtuse-angled corners 23 of the other block with the lateral grooves 31 and 32 interposed therebetween.

The widths of the lateral grooves 31 and 32 are narrower than those of the main groove 11. Specific numerical values for the widths of the lateral grooves 31 and 32 are, for example, 2 mm or more and 4 mm or less. The depths of the lateral grooves 31 and 32 are 20% or more and 35% or less of the depth of the main groove 11.

As shown in FIGS. 1 to 3, a sipe 33 continuous from the bottom 36 of the lateral groove 31 is provided on the bottom 36 side of the lateral groove 31. The sipe 33 is narrower than the lateral groove 31. The specific value of the width of the sipe 33 is, for example, 0.6 mm or more and 1.5 mm or less. The total depth of the lateral groove 31 and the sipe 33, that is, the depth from the opening end 37 of the lateral groove 31 to the contact patch to the bottom 35 of the sipe 33 is shallower than the depth of the main groove 11.

As the sipe 33 becomes deeper, it moves away from the acute-angled corner 22 and inclines in a direction of entering under the obtuse-angled corner 23, thereby twisting. Explaining in detail with reference to FIGS. 1 to 3, the sipe 33 between the two center-side blocks 21a and 21b adjacent to each other in the tire circumferential direction moves away from the acute-angled corner 22a as it gets deeper on the tire equatorial CL side. It is inclined in the direction of entering under the corner portion 23b at an acute angle. Further, on the ground contact end E side, the sipe 33 enters under the obtuse-angled corner portion 23a as it gets deeper, and is inclined in a direction away from the acute-angled corner portion 22b. The inclination angle θ of the sipe 33 continuously changes from the end on the tire equator CL side of the sipe 33 to the end on the ground contact end E side. As a result, the sipe 33 is twisted.

In other words, with respect to the center side block 21a on one side in the tire circumferential direction, the sipe 33 inclines in the direction away from the acute-angled corner 22a as it becomes deeper on the acute-angled corner 22a side, resulting in an obtuse angle. On the corner portion 23a side of the above, the angle is inclined so as to enter under the obtuse angle portion 23a as it becomes deeper. As a result, inevitably, with respect to the center side block 21b on the other side in the tire circumferential direction, the sipe 33 is inclined in the direction of entering under the obtuse angle portion 23b as it becomes deeper on the obtuse angle corner portion 23b side. On the side of the acute-angled corner 22b, the deeper the angle, the more inclined the angle is from the acute-angled corner 22b. The sipe 33 is twisted because the inclination angle θ of the sipe 33 continuously changes from the end on the tire equator CL side of the sipe 33 to the end on the ground contact end E side.

The inclination angle θ of the sipe 33 is larger as it is closer to the acute-angled corners 22 and the obtuse-angled corners 23, that is, on both sides in the tire width direction. It is desirable that the magnitude of the inclination angle θ with respect to the direction perpendicular to the ground plane of the sipe 33 is 15 ° or less at the maximum.

The depth of the sipe 33 may be partially shallow. The shallow portion of the sipe 33 is called a tie bar 38. The tie bar 38 is formed over the entire width direction of the sipe 33, thereby connecting the blocks 21 and 21 on both sides of the lateral groove 31 in the tire circumferential direction. As shown in FIG. 4, the position of the tie bar 38 is preferably the center position of the sipe 33.

In FIG. 4, the end of the sipe 33 on the main groove 11 side is open to the main groove 11. Further, the end portion of the sipe 33 on the shoulder side block 26 side is closed within the range of the lateral groove 31 in the tire width direction. However, the end portion of the sipe 33 on the main groove 11 side may not be opened in the main groove 11 and may be closed within the range of the lateral groove 31 in the tire width direction.

A sipe 39 having the same characteristics as the sipe 33 on the bottom 36 side of the lateral groove 31 is also provided on the bottom side of the lateral groove 32 on the grounding end E side.

Further, the center land portion 40 on the left side has the same characteristics as the center land portion 20 on the right side. That is, the center land portion 40 on the left side is also provided with a narrow groove 50 extending in the tire circumferential direction, and two rows of blocks consisting of a center side block 41 and a shoulder side block 46 sandwiching the fine groove 50 are formed. .. Lateral grooves 51 and 52 having a depth of 20% or more and 35% or less of the main groove 11 are provided between the blocks adjacent to each other in the tire circumferential direction. Further, on the bottom side of the lateral grooves 51 and 52, sipes 53 and 54 having the same width and depth as the sipes 33 are provided. The sipes 53 and 54 are inclined in a direction away from the acute-angled corner 42 as they become deeper on the acute-angled corner 42 side of the block, and below the obtuse-angled corner 43 as they become deeper on the obtuse-angled corner 43 side of the block. It tilts in the direction of entry and is twisted accordingly. A tie bar may also be provided on the sipes 53 and 54.

The structures of the two shoulder land portions 12 and 13 are not limited to those in FIG.

Heel-and-toe wear is less likely to occur with the pneumatic tire of this embodiment. With conventional pneumatic tires, the lateral grooves between the blocks are deep enough and there are no sipes on the bottom side of the lateral grooves. However, in the pneumatic tire of the present embodiment, the depths of the lateral grooves 31, 32, 51, and 52 are only 20% or more and 35% or less of the depth of the main groove 11. Instead of the lateral grooves 31, 32, 51, 52 being shallow in this way, sipes 33, 39, 53, 54 narrower than the lateral grooves 31, 32, 51, 52 are provided on the bottom side of the lateral grooves 31, 32, 51, 52. Has been done. As a result, the rigidity of the blocks on both sides of the lateral grooves 31, 32, 51, and 52 in the tire circumferential direction is increased as compared with the conventional pneumatic tire, and heel-and-toe wear is less likely to occur in these blocks.

Further, in general, when the block has an acute-angled corner portion and an obtuse-angled corner portion on both sides in the tire circumferential direction, the acute-angled corner portion is more likely to wear than the obtuse-angled corner portion. However, in the present embodiment, the sipes 33, 39, 53, 54 incline in the direction away from the acute-angled corners 22, 42 as they become deeper on the acute-angled corners 22, 42, and the obtuse-angled corners 23, 43 side. Then, as it becomes deeper, it is inclined in the direction of entering below the obtuse angled corners 23 and 43, so that the rigidity near the acute-angled corners 22 and 42 increases and the rigidity near the obtuse angled corners 23 and 43 decreases. There is. As a result, the vicinity of the acute-angled corners 22 and 42, which have been easily worn in the past, is relatively less likely to be worn, and heel-and-toe wear is less likely to occur in the block.

Further, since the sipes 33, 39, 53, and 54 are partially shallow to form a tie bar, the rigidity in the vicinity of the tie bar in the block is increased. This makes it difficult for the block to wear. In particular, when the sipes 33, 39, 53, 54 are long in the tire width direction, the rigidity of the block tends to decrease, but the tie bar prevents the decrease in the rigidity of the block.

The above embodiments are examples, and the scope of the invention is not limited thereto. Various changes, substitutions, omissions, etc. can be made to the above embodiments without departing from the gist of the invention.

First, the land portion provided with the lateral groove and the sipe of the present embodiment may be composed of a plurality of blocks having acute-angled corners formed on one side in the tire width direction and obtuse-angled corners formed on the other side. .. The number of block rows formed by the blocks in the land portion sandwiched between the two main grooves 11 is not limited to the two rows as in the above embodiment, and may be one row or three or more rows. You may.

As an example, FIG. 5 shows a tread pattern in the case where the land portion sandwiched between the two main grooves 11 is composed of one row of blocks. In the tread pattern of FIG. 5, the center land portion 120 on the right side is provided with a lateral groove 131 having a depth of 20% or more and 35% or less of the main groove 11. Further, on the bottom side of the lateral groove 131, a sipe 133 having the same width and depth as the sipe 33 of the above embodiment is provided. The sipe 133 is inclined in a direction away from the acute-angled corner 122 as it gets deeper on the acute-angled corner 122 side of the block, and enters under the obtuse-angled corner 123 as it gets deeper on the obtuse-angled corner 123 side of the block. Tilt in the direction, thereby twisting. The lateral groove 131 and the sipe 133 are open to the main grooves 11 on both sides in the tire width direction. A tie bar may also be provided on this sipe 133. The center land portion 140 on the right side on the left side is also provided with a lateral groove 151 and a sipe 153 similar to the center land portion 120 on the right side. Even when the block row sandwiched between the two main grooves 11 is one row as described above, the rigidity of the block is increased and heel-and-toe wear is less likely to occur in the block as in the above embodiment.

Further, in FIGS. 2 and 3 of the above-described embodiment, the sipe 33 extends straight from the opening end 34 to the lateral groove 31 to the bottom portion 35. However, as shown in FIG. 6, the sipe 233 extends in a direction perpendicular to the ground contact surface by a certain distance from the opening end 34 to the lateral groove 31, bends at the fixed distance from the opening end 34, and is bent from the opening end 34. The portion from the fixed distance position to the bottom 35 may be inclined. When the sipe 233 is bent at a certain distance from the opening end 34 as shown in FIG. 6, the portion from the bent position to the bottom 35 is separated from the acute-angled corner 22 of the block 21 and the block 21 is bent. It is inclined so as to approach the corner 23 of the obtuse angle.

When the sipe 233 is bent at a certain distance from the opening end 34 as shown in FIG. 6, the inclination angle θ is the line connecting the opening end 34 of the sipe 233 and the bottom 35 of the sipe 233 and the ground plane. It is the angle formed by the line perpendicular to. Similar to the above embodiment, it is desirable that the magnitude of the inclination angle θ is 15 ° or less at the maximum. Further, even when the sipe 233 is bent at a certain distance from the opening end 34 as shown in FIG. 6, the depth of the sipe 233 is partially shallowed at the center position of the sipe 233 or the like to form a tie bar. You may have.

Further, in the above embodiment, the sipe is not provided on the bottom side of the narrow grooves 30 and 50 extending in the tire circumferential direction. However, a sipe continuous from the bottom of the fine grooves 30 and 50 may also be provided on the bottom side of the fine grooves 30 and 50. This sipe is narrower than the narrow grooves 30 and 50. Further, the depth obtained by adding the narrow grooves 30 and 50 and the sipe is shallower than the depth of the main groove 11. This sipe inclines in the direction away from the acute-angled corners 22 and 42 as it gets deeper on the acute-angled corners 22 and 42 of the block, and the obtuse-angled corner 23 as it gets deeper on the obtuse-angled corners 23 and 43. It may be tilted in a direction that goes under 43, thereby twisting. In order to ensure the rigidity of the block, the sipe on the bottom side of the narrow grooves 30 and 50 is not connected to the sipe on the bottom side of the lateral grooves 31, 32, 51 and 52.

The uneven wear resistance of the pneumatic tires of Examples, Reference Examples and Comparative Examples shown in Table 1 and the pot removal property in vulcanization molding were evaluated. The tread of the pneumatic tire used for the evaluation had the same block row as in FIG. 1 of the above embodiment. In the following description and FIG. 7, for convenience, the lateral groove is indicated by reference numeral 31 and the sipe is indicated by reference numeral 33. However, the features shown in the following description and FIG. 7 are all the lateral grooves in one pneumatic tire. It is assumed that the lateral grooves 31, 32, 51, 52) and the sipe (sipe 33, 39, 53, 54 in FIG. 1) are common in FIG.

As shown in Table 1 and FIG. 7, the presence / absence of the sipe 33 and the cross-sectional shapes of the lateral groove 31 and the sipe 33 were different in the examples, reference examples, and comparative examples. The total depth r in Table 1 is the sum of the lateral groove depth p and the sipe depth q. Further, the sipes 33 of Reference Examples 2 and 3 are inclined in a direction away from the acute-angled corners as they become deeper on the acute-angled corners of the block, and on the obtuse-angled corners of the block, the obtuse-angled corners become deeper. It tilted in the direction of going down, which caused it to twist. Further, the maximum sipe inclination angle θ in Table 1 is the magnitude of the inclination angle of the sipe 33 with respect to the direction perpendicular to the ground plane at the position where the sipe 33 is most inclined. The width and main groove depth of the lateral groove 31 were the same in all the examples, reference examples and comparative examples, and the width of the lateral groove 31 was 3 mm and the main groove depth was 14 mm.

In the evaluation of uneven wear resistance, the tire size was 205 / 85R16, the mounting rim size was 16 × 5.50, and the internal pressure was 600 kPa. The vehicle was equipped with pneumatic tires to be evaluated, the load was 12.6 kN, and the vehicle was run for 12000 km. After running, the wear difference between the stepping side and the kicking side of the center side block was measured. Then, the average value of the wear difference between the two pneumatic tires was obtained, and the average value was indexed. The index is set so that the index of Comparative Example 1 is 100, and the smaller the wear difference, the smaller the index.

In the evaluation of the pot pullability, after the vulcanization molding of the pneumatic tire was completed and the pneumatic tire was taken out from the mold, the presence or absence of a rubber defect in the vicinity of the sipe 33 was confirmed. This confirmation was performed for a plurality of pneumatic tires, the occurrence rate of defects was determined, and the occurrence rate was defined as the ability to pull out the hook.

The evaluation results are shown in Table 1, and it was confirmed that the uneven wear resistance was improved when the sipe 33 was provided on the bottom side of the lateral groove 31. Further, it was confirmed that when the sipe 33 is twisted as described above, the uneven wear resistance is further improved. Further, it was confirmed that the hook removal property was not extremely deteriorated even if the sipe 33 on the bottom side of the lateral groove 31 was twisted, and was good when the sipe maximum inclination angle θ was 15 degrees or less.

10 ... Tread, 11 ... Main groove, 12, 13 ... Shoulder land, 20 ... Center land, 21 ... Center side block, 22 ... Acute angle corner, 23 ... Obtuse angle corner, 26 ... Shoulder side block, 30 ... Fine groove, 31 ... Horizontal groove, 32 ... Horizontal groove, 33 ... Sipe, 34 ... Sipe 33 opening end, 35 ... Sipe 33 bottom, 36 ... Horizontal groove 31 bottom, 37 ... Horizontal groove 31 opening end, 38 ... Tie bar, 39 ... Sipe, 40 ... Center land, 41 ... Center side block, 42 ... Acute angle corner, 43 ... Obtuse angle corner, 46 ... Shoulder side block, 50 ... Fine groove, 51 ... Horizontal groove, 52 ... Horizontal groove, 53 ... Sipe, 54 ... Sipe, 120 ... Center land, 122 ... Sharp corner, 123 ... Obtuse angle, 131 ... Horizontal groove, 133 ... Sipe, 140 ... Center land, 151 ... Horizontal groove, 153 ... Sipe, 233 ... Sipe, CL ... Tire equatorial line, E ... Grounding edge

Claims (2)

A plurality of blocks are lined up in the tire circumferential direction in the land portion partitioned by the main groove extending in the tire circumferential direction, and the lateral groove between the blocks adjacent to the tire circumferential direction is at a depth of 20% or more and 35% or less of the main groove. A sipe narrower than the lateral groove is provided on the bottom side of the lateral groove .
By extending the lateral groove diagonally with respect to the tire width direction, an acute-angled corner portion is formed on one side in the tire width direction of the block, and an obtuse-angled corner portion is formed on the other side.
As the sipe becomes deeper, it tilts toward the corner of the acute angle away from the corner of the acute angle, and at the corner of the obtuse angle, it tilts toward the bottom of the corner of the obtuse angle, thereby twisting. Pneumatic tires. The pneumatic tire according to claim 1 , wherein the sipes are partially shallow.

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